For some special applications it is desirable to provide very long conveyor belts in the range of 150-200 meters or even longer. This is usually done by arranging a plurality of smaller conveyor units in an array in that when conveyor belts reach certain lengths a number of undesirable problems arise.
One of these problems is that as the conveyor belt reaches a certain length loads on the conveyor belt will create horizontal wave actions in the belt such that for example personnel using the conveyor belt as a transporter will feel a movement in the surface which is very undesirable. Therefore historically the long conveyor belt has been made up of a number of conveyor structures, but this, in turn, creates the problem that if a person is working or walking on this belt, special attention has to be paid when switching from one conveyor belt to the adjacent conveyor belt. For example in the automobile industry in order to avoid accidents safety zones have been created adjacent to the ends of the conveyor belts where workers are not allowed to perform their tasks. This leads to wasted space and extra long assembly lines which increases the overall costs of the manufacturing facility.
In the art systems have been proposed in for example U.S. Pat. No. 5,934,862, U.S. Pat. No. 3,994,390, U.S. Pat. No. 3,858,473, GB 1 500 909 and WO2008/070444. Common for all these systems is the fact that they use one or two independent sub-belts to propel the main conveyor belt, and thereby to distribute the engagement force provided by the driving means—typically an electric motor turning one or more sprocket wheels engaging the underside of a belt.